The objective of this project is to examine the mechanism(s) by which pituitary diabetogenic substances produce their metabolic effects. The first of these is a pituitary substance which is a common contaminant of hGH preparations; we have been able to separate this factor from hGH so that the remaining hGH was no longer diabetogenic in the dog. In contrast, the diabetogenic factor caused severe glucose intolerance and hyperinsulinemia at a dosage level of 50 micrograms/kg. The effects of the substance persisted for as long as 34 hours. The second of these, a subtilisin cleaved form of intact monomeric hGH, exhibited hyperglycemic properties similar to those of the naturally occurring factor. These two preparations will be used in the proposed study. Three major approaches will be used to examine the hyperglycemic action of the above diabetogenic pituitary peptides: 1) The effects of the diabetogenic substances on glucose and FFA metabolism, amino acid transport and the release of glucagon and insulin will be studied. Any effects of these substances will be compared to those induced by clinical grade hGH and also hGH preparations from which the naturally present diabetogenic factor has been removed; 2) The effects of these agents on structural and functional properties of plasma membranes from insulin sensitive and insulin secreting cells will also be determined. Amphiphilic spin probes, incorporated into either isolated plasma membranes or membranes of intact cells, should yield electron spin resonance spectra which are sensitive to the fluidity of lipid domains. Any changes in lipid fluidity will be correlated with alterations in membrane lipid composition and membrane-bound enzymatic activities which might be induced by the diabetogenic agents. 3) We will also examine effects of the diabetogenic substances on the insulin binding capacity of isolated membranes. Such an integrated analysis of the mechanism(s) by which the diabetogenic substances produce their effects may help to determine the role which the pituitary gland plays in diabetes mellitus.